F: R -> R, f(x) = ax + b;
f(1) = 8 => a + b = 8;
f(2) = 14 => 2a + b = 14 => a = 6 and b =2;
f(3) = 20 => 6*3 + 2 = 20 True;
f(4) = 26 => 4*6 + 2 = 26 True;
then, f:R -> R, f(x) = 6x + 2;
Answer: 48
Step-by-step explanation: COB and DOA are vertical angles. This means the two of them have the same measure. Because we know the measuremen of DOA, we can easily find the measuremen for COB since these angles are the same, so COB is 48 degrees.